Athletes often have to compete late in the evening, when they are no longer able to perform at their best. As reported in the journal Frontiers in Physiology, however, researchers from the University of Basel have shown that ...

Oral melatonin can protect the small intestine in rats subjected to radiotherapy of the tongue, according to a study published April 12, 2017 in the open-access journal PLOS ONE by Germaine Escames from Universidad de Granada, ...

In our modern times, many of us sit up late into the night, watching TV, fiddling with our smartphones, or reading a book by lamplight. Getting up to the sound of the morning alarm isn't easy. Now, researchers reporting in ...

Some people adapt easily to shift work, but not everyone can handle constant disruptions to their daily rhythm. Finnish researchers have now found that a melatonin receptor gene influences tolerance to shift work.

The circadian rhythm, or circadian clock, is an internal mechanism that drives the 24-hour cycles that tell our bodies when to sleep, wake and eat — and now, new research has found that bacteria living within the gut ...

A few weeks ago, thousands of researchers gathered in Denver, Colorado for the SLEEP 2016 meeting. Skimming over the abstracts, one can find diverse research topics like "Need better sleep? Consider the cognitive shuffle," ...

Melatonin

Melatonin i/ˌmɛləˈtoʊnɪn/, also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring compound found in animals, plants, and microbes. In animals, circulating levels of the hormone melatonin vary in a daily cycle, thereby allowing the entrainment of the circadian rhythms of several biological functions.

Many biological effects of melatonin are produced through activation of melatonin receptors, while others are due to its role as a pervasive and powerful antioxidant, with a particular role in the protection of nuclear and mitochondrial DNA.

In mammals, melatonin is secreted into the blood by the pineal gland in the brain. Known as the "hormone of darkness," it is secreted in darkness in both day-active (diurnal) and night-active (nocturnal) animals.

It may also be produced by a variety of peripheral cells such as bone marrow cells, lymphocytes, and epithelial cells. Usually, the melatonin concentration in these cells is much higher than that found in the blood, but it does not seem to be regulated by the photoperiod.

Research has shown that when bird chicks ingest melatonin-rich plant feed, such as rice, the melatonin binds to melatonin receptors in their brains. No food has been found to elevate plasma melatonin levels in humans.

Products containing melatonin have been available over-the-counter as dietary supplements in the United States since the mid-1990s. In many other countries, the over-the-counter sale of this neurohormone is not permitted or requires a prescription, and the U.S. Postal Service lists unapproved melatonin preparations among items prohibited by Germany.